The Red Valve Company has developed a way to use its check valve technology to improve water quality in distribution-system reservoirs. The Tideflex® Mixing System (TMS) combine Tideflex® Check Valves and a simple piping manifold that, when installed inside a water storage tank, improves overall circulation and mixing, eliminating stagnation and hydraulic short-circuiting.
The City of Antioch, Calif., was one of the first to test the TMS when it launched a $350,000 upgrade to its 33-year-old finished water storage reservoir. Like many older tanks, this circular three million gallon reservoir was designed with a single protrusion that acted as a common inlet and outlet. While this type of design adequately supplies the required hydraulics of the distribution system, it will not necessarily maintain water quality within the reservoir.
Many finished water storage reservoirs have problems with deteriorating water quality as a result of short-circuiting, where water outside the inlet/outlet area of influence becomes stagnant, causing the disinfectant residual to decrease. The loss of disinfectant residual and long detention times can result in the multiplication of bacteria, formation of disinfection byproducts and nitrification in chloraminated systems.
The TMS was designed to eliminate stagnation through enhanced mixing in finished water storage tanks. The system makes use of two sets of check valves and a single piping manifold. The first set of valves discharges during filling, and the second set discharges during draining. The two sets of valves are positioned on the manifold to maximize the distance between the inlet and outlet, thereby eliminating short-circuiting and improving mixing. The TMS is a lower cost solution for achieving a separate inlet/outlet than a dual-pipe system, which requires two tank protrusions and additional excavation, pipe, valves and fittings.
The passive valves are constructed of NSF 61-approved elastomers and have no mechanical parts. Since they require only differential head to operate, no outside energy source is required, keeping operational costs to a minimum. They won't freeze shut and are designed to seal around entrapped debris.
City of Antioch Plant Superintendent Jon Billeci decided to see for himself whether the valves would truly close drop-tight around entrapped debris. He entered the tank and tried to lodge one of the valves open with a heavy-duty flashlight and was amazed at the valve's ability to seal around such a large obstruction.
Another point of skepticism for Billeci was the rubber-like construction of the Tideflex® valve. The City of Antioch uses chloramines, which contain a small amount of ammonia, as the primary disinfectant in its water storage tanks. Certain types of rubber will deteriorate upon contact with ammonia. Billeci took curtains made of Hypalon®, the elastomer that would comprise the check valves proposed for installation, and soaked them in pure ammonia to simulate the effect that the diluted ammonia would have on the valve over a long period of operation.
"They looked the same when I pulled them out as they did when I put them in," he said. "I was very satisfied with the material."
The system can be installed in reservoirs, standpipes and elevated tanks of all shapes and capacities, whether they are newly constructed or several decades old.
